Volcanic plug

A mass of magma that hardens inside a volcano’s conduit. It may remain standing as a landform when surrounding volcanic rock erodes.

Volcanic conduit: The passage through which magma travels from a volcanic reservoir toward the surface. A plug forms when magma hardens inside this passage.
Volcano: An opening in Earth’s crust, commonly with a mountain or other landform built by erupted material. A plug occupies the internal passage of a volcano.
Shiprock: A volcanic landform in New Mexico, consisting of a central rock mass and radiating dikes. Its resistant central mass is widely interpreted as the exposed core of an eroded volcano.
Lava flow: A mass of molten rock that erupts and moves across Earth’s surface before cooling. A flow spreads at the surface, unlike magma solidifying inside a conduit.
Magma: Molten or partly molten rock beneath Earth’s surface, containing dissolved gases and crystals. It is the material that cools and hardens to form a plug.
Volcanic vent: An opening through which volcanic gases, lava, or fragmented material reaches the surface. A vent lies at the surface end of the conduit a plug may seal.
Devils Tower: A prominent igneous rock formation in Wyoming, rising above the surrounding landscape. Its origin as a volcanic plug or shallow intrusion remains debated.
Dike (geology): A tabular igneous intrusion that cuts across pre-existing rock layers. A dike fills a fracture rather than the volcano’s central conduit.
Igneous rock: Rock formed when molten rock cools and solidifies. A volcanic plug is an intrusive body of solidified igneous rock.
Volcanic crater: A basin-shaped depression around a volcanic vent, formed by eruptions or collapse. A plug may lie beneath the crater at the volcano’s central vent.

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Mount KenyaRelated: Erosion exposed resistant volcanic rock that helps form Mount Kenya’s highest peaks.